and that's the challenge for city authorities. providing clean water, sewage treatment, electricity, housing and waste disposal for millions of people every day is proving a logistical nightmare. the south korean capital seoul is taking a positive approach to this huge task. there, waste management authorities are beginning to rely on sophisticated recycling techniques and reclaiming precious resources to fuel this metropolis. we take a look at seoul's attempt to make city life more sustainable. >> the district of myeongdong, one of seoul's main shopping areas, is teeming with customers almost every evening. south korean teenagers in particular are keen to keep up with the latest fashions and trends. while the masses shop till they drop, others are getting to work on the night shift. seoul's waste collectors handle with the trash produced by the city's consumerist society. an estimated 20,000 people living in the asian megacity live or earn extra income from recycling what others throw away. they concentrate on the entertainment a